The present invention relates to a method and system for the testing of a joint which joins at least two members. More specifically, the present invention relates to a method and system for the non-destructive testing of a joint that joins a fastener or other first member with a second member.
In a variety of manufacturing and other applications, fasteners or other members are joined to a member or substrate with joints such as adhesives, welds, or the like. For example, and without limitation, in the automotive vehicle industry, fasteners such as nuts or other fasteners are often welded to portions of a vehicle such that bolts or other fasteners may later be threaded into or otherwise attached to those nuts or other fasteners. In one particular non-limiting example, an automotive vehicle may include a cross member on a floor of the vehicle, wherein the cross member includes nuts that are welded to the cross member such that bolts may be attached or fastened to those nuts to anchor a vehicle seat or other structure to the cross member.
To help assure desired quality, it is preferable that the joint between such a fastener and an associated joint member be tested. Destructive testing techniques are popular, but these require the destruction of either the joints, members or fasteners, thereby rendering the assembly a waste. There is, therefore, a need for a substantially non-destructive method and system for reliably and reproducibly testing joints which join members such as fasteners to other members or substrates.
Even more specifically, in the automotive vehicle industry, there is a need to test the quality of a joint such as a weld or an adhesive joint which joins fasteners such as nuts, bolts, studs or the like to other members of the vehicle. It is particularly desirable to test the quality of production joints regularly during the vehicle assembly process, in an efficient and cost-effective manner.
According to a first aspect of the present invention, there is provided a method for testing first members which are joined to second members with joints. The method includes collecting reference data relating to strain or displacement of a first joint which attaches a first member to a second member as a first load is exerted upon the first joint, the first joint having a first elastic limit and the first load straining the first joint beyond the first elastic limit, and the first load placing a tensile stress upon the first joint; collecting test data relating to strain of a second joint which attaches a third member to a fourth member as a second load is exerted upon the second joint, the second joint having a second elastic limit, the second load straining the second joint only within the second elastic limit and the second load placing a tensile stress upon the second joint; and comparing the test data to the reference data to determine if the test data is within a predetermined tolerance limit from the reference data.
According to a second aspect of the present invention, there is disclosed a method for testing a fastener which is attached with a joint to a generally planar member having a hole, the fastener attached to the member adjacent and/or covering the hole. The method includes exerting a load upon the joint with a contacting member that can selectively extend through the hole, the load causing a tensile stress upon the joint, and the method includes monitoring the strain or displacement of the joint as the load is exerted.
According to a third aspect of the present invention, there is disclosed a system for testing fasteners which are attached to members. The system includes a punch which is capable of exerting a load upon a joint which attaches a fastener to a member; a load cell operatively connected to the punch, the load cell capable of determining the amount of the load exerted by the punch; a support member for supporting the first member as the load is exerted upon the joint; and a deflection meter which is capable of measuring the amount of deflection experienced by the joint due to the load.
These and other objects, aspects, and advantages of the present invention will become apparent upon reading the following detailed description in combination with the accompanying drawings.